JP2012138347A - Power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage device capable of improving performance such as higher discharge capacity and hardly causing deterioration due to peeling or the like of an active material layer.SOLUTION: In an electrode for a power storage device, phosphorus-doped amorphous silicon is used for an active material layer over a collector as a material that can be alloyed with lithium, and a niobium oxide is formed over the active material layer as a layer containing niobium. Accordingly, the capacity of the power storage device can be increased. Furthermore, the cycle characteristics and charge/discharge efficiency of the power storage device can be improved.

Description

The present invention relates to a power storage device.

Note that the power storage device refers to all elements and devices having a power storage function.

In recent years, various power storage devices such as lithium secondary batteries, lithium ion capacitors, and air batteries have been developed. In particular, lithium secondary batteries that charge and discharge by moving lithium ions between a positive electrode and a negative electrode have attracted attention as secondary batteries with high output and high energy density.

An electrode for a power storage device is manufactured by forming an active material layer on one surface of a current collector. The active material layer is formed of an active material such as carbon or silicon capable of storing and releasing ions serving as carriers. For example, when an active material layer is formed of silicon or silicon to which phosphorus is added, the theoretical capacity is larger than that of forming an active material layer of carbon, which is superior in terms of increasing the capacity of a power storage device (for example, patents). Literature 1.).

However, it is known that silicon as an active material expands or contracts when the lithium ions are occluded or released. Therefore, with the charging / discharging of the battery, the active material layer is pulverized and detaches from the current collector. As a result, the current collecting property in the electrode is lowered, and the charge / discharge cycle characteristics are deteriorated. As a countermeasure against this, there is a method of suppressing the collapse of silicon by coating the surface of the active material layer with carbon, copper, nickel, etc. However, when these coatings are performed, the reactivity between lithium and silicon is reduced. Therefore, there is a drawback that the charge / discharge capacity is reduced.

Japanese Patent Laid-Open No. 2001-210315

An object of one embodiment of the present invention is to provide a power storage device that can increase charge / discharge capacity and improve performance of the power storage device such as cycle characteristics.

In an electrode for a power storage device, a material that is alloyed with lithium as an active material layer on a current collector, and by forming a layer containing niobium on the active material layer, the capacity of the power storage device can be increased. Furthermore, cycle characteristics and charge / discharge efficiency can be improved.

The layer containing niobium is preferably formed of niobium oxide or niobium nitride. Further, it may contain a niobium lithium alloy, for example, Li ₂ Nb ₂ O ₅ . The layer containing niobium may be amorphous or may have crystallinity.

The Li ₂ Nb ₂ O ₅ is formed by reaction of Nb ₂ O ₅ and Li by a battery reaction. Furthermore the _Li 2 _Nb 2 _{O 5} may be retained in the subsequent charge and _discharge, Li 2 _Nb 2 _{O 5} Li is desorbed from the, may serve as _Nb 2 _{O 5.} Thus, Li ₂ Nb ₂ O ₅ is formed on the active material layer, so that Li ₂ Nb ₂ O ₅ acts as a stable inorganic SEI instead of organic SEI (Solid Electrolyte Interface), thereby There are effects such as lowering resistance, improving lithium diffusibility, and relaxing volume expansion of the active material layer.

The active material is preferably a material that can be alloyed with lithium. For example, a material containing silicon, tin, aluminum, or germanium can be used. Furthermore, it is preferable that phosphorus or boron is added to the active material. By using these materials, the capacity of the power storage device can be increased.

The active material may be amorphous, microcrystalline, polycrystalline, or single crystalline. Further, for example, in the case where silicon is used as the active material, a crystalline silicon region and a whisker-like crystalline silicon region having a plurality of protrusions protruding on the crystalline silicon region can be provided. Furthermore, a structure having amorphous silicon around crystalline silicon may be used. The whisker-like crystalline silicon region may have a protrusion having a bent or branched portion.

In the above, the crystalline silicon layer having the whisker-like crystalline silicon region is formed by a thermal CVD (CVD: Chemical Vapor Deposition) method or low pressure chemical vapor deposition on a current collector using a deposition gas containing silicon. It can be formed by (LPCVD: Low pressure chemical vapor deposition) method or plasma CVD method.

As described above, the surface area of the active material is increased by including the crystalline silicon region and the whisker-like crystalline silicon region having a plurality of protrusions protruding on the crystalline silicon region as the active material layer. By increasing the surface area of the active material, the amount of carrier ions such as lithium ions in the power storage device stored in the active material per unit time or the amount of carrier ions released from the active material per unit time Increase with. Since the amount of occlusion or release of carrier ions per unit time increases and the amount of occlusion or release of carrier ions at a high current density increases, the discharge capacity or charge capacity of the power storage device can be increased.

As the current collector, a highly conductive material such as a metal element typified by platinum, aluminum, or copper can be used. The current collector may be formed using a metal element that forms silicide by reacting with silicon.

The electrolyte layer formed between the negative electrode in the power storage device and the positive electrode facing the negative electrode can be formed of a liquid or a solid, and the electrolyte layer may contain niobium.

In one embodiment of the present invention, a multilayer structure such as a current collector, an active material layer, and a layer containing niobium can be used, whereby each layer is formed using the current collector, the active material layer, and the layer containing niobium. When the substances to be bonded are bonded, the structure can be strengthened. For this reason, it is difficult for the structure to be destroyed due to the volume change of the active material layer accompanying charge / discharge. As a result, even when a charge / discharge cycle is passed, the destruction of the active material layer is suppressed, so that an increase in resistance inside the battery and a decrease in capacity can be suppressed.

Further, in one embodiment of the present invention, the electrode of the power storage device can be formed by a coating method. For example, by applying a slurry in which silicon particles are mixed as an active material on a current collector, followed by firing to form a coated electrode, and forming a layer containing niobium on the coated electrode, a high capacity and good cycle A coated electrode having characteristics can be formed.

In one embodiment of the present invention, a material containing niobium can be used as an additive for a coating electrode used in a power storage device.

Further, according to one embodiment of the present invention, charge and discharge efficiency is improved, and CV (constant voltage) charging is not necessary. Therefore, the charging time can be shortened, and the cycle characteristics of the negative electrode material can be further improved.

According to one embodiment of the present invention, a power storage device with improved battery performance such as an increase in discharge capacity or charge capacity can be provided. Further, it is possible to provide a power storage device in which deterioration of the power storage device due to peeling of the active material layer or the like in the electrode is reduced.

It is a figure which shows the electrode of an electrical storage apparatus. It is a figure which shows the preparation process of the electrode of an electrical storage apparatus. It is a figure which shows the electrode of an electrical storage apparatus. It is a figure which shows the preparation process of the electrode of an electrical storage apparatus. 2A and 2B are a plan view and a cross-sectional view of one embodiment of a power storage device. It is a perspective view of one form of application of a power storage device. It is a figure which shows the example of a structure of a radio | wireless electric power feeding system. It is a figure which shows the example of a structure of a radio | wireless electric power feeding system. FIG. 11 illustrates a manufacturing process of a power storage device. It is a figure which shows the battery characteristic of an electrical storage apparatus.

An example of an embodiment of the present invention will be described below with reference to the drawings. However, the present invention is not limited to the following description, and it is easily understood by those skilled in the art that modes and details can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description of the embodiments below. Note that in the description of the drawings, the same reference numerals may be used in common in different drawings. In addition, the same hatch pattern is used when referring to the same thing, and there is a case where no reference numeral is given.

(Embodiment 1)
In this embodiment, an electrode of a power storage device which is one embodiment of the present invention and a manufacturing method thereof will be described with reference to FIGS.

FIG. 1 is a diagram illustrating one embodiment of an electrode of a power storage device. An electrode of the power storage device illustrated in FIG. 1 includes a current collector 101, an active material layer 103 provided over one surface of the current collector 101, and a layer 109 containing niobium provided over the active material layer 103. Have.

The current collector 101 is formed using a material having conductivity that can be used as a current collector for a negative electrode and heat resistance for a subsequent heat treatment as appropriate. Examples of the conductive material that can be used as the current collector include, but are not limited to, copper, platinum, aluminum, nickel, tungsten, molybdenum, titanium, and iron. Note that when aluminum is used for the current collector, an aluminum alloy to which an element for improving heat resistance such as silicon, titanium, neodymium, scandium, or molybdenum is added is preferably used. Alternatively, an alloy of the above conductive material may be used.

Alternatively, the current collector 101 may be formed using a metal element that forms silicide by reacting with silicon. Examples of metal elements that react with silicon to form silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, nickel, and the like.

An oxide conductive material can be used as the current collector 101. Typical examples of the oxide conductive material include indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, and titanium oxide. Indium oxide containing, indium tin oxide containing titanium oxide, indium tin oxide, indium zinc oxide, indium tin oxide added with silicon oxide, or the like can be given. Note that the current collector 101 may have a foil shape, a plate shape, or a net shape. In the case of such a shape, since the shape can be maintained by the current collector 101 alone, it is not necessary to use a support substrate or the like.

The active material layer 103 is preferably formed using a material that is alloyed with ions that are carriers of charge. The ions that are charge carriers may be alkali metal ions such as lithium and sodium, alkaline earth metal ions such as calcium, strontium, and barium, beryllium ions, or magnesium ions, and lithium is preferably used. For the active material layer 103, silicon, tin, aluminum, germanium, or the like can be used as a material that can be alloyed with lithium, for example.

In the case where silicon is used for the active material layer, a silicon layer can be formed over the current collector 101 by a plasma CVD method or the like. At this time, when forming the silicon layer, it is preferable that hydrogen is not contained in the material gas as much as possible. As a result, defects such as dangling bonds formed in silicon increase, and lithium ion insertion / extraction reactions can easily occur.

The layer 109 containing niobium provided over the active material layer 103 can be formed using niobium oxide or niobium nitride. Instead of niobium, vanadium, tantalum, tungsten, zirconium, molybdenum, hafnium, chromium, titanium oxide, or nitride can be used. Further, the crystallinity may be any of amorphous, polycrystalline or single crystal.

Next, a method for forming the electrode will be described with reference to FIG.

First, as illustrated in FIG. 2A, the active material layer 103 is formed over the current collector 101. For example, a titanium sheet may be used as the current collector 101, and a silicon layer may be formed as the active material layer 103 over the current collector 101 by a plasma CVD method. The silicon layer may contain an impurity element that generates carriers, such as phosphorus or boron. For example, in order to include phosphorus in the silicon layer, phosphine may be included in the material gas. Note that the crystallinity of the silicon layer is not particularly limited, and the silicon layer may be amorphous or may have crystallinity. For example, amorphous silicon, microcrystalline silicon, or polycrystalline silicon can be used. Here, crystallization may be performed on the silicon layer. When crystallization is performed on the silicon layer, the silicon layer may be subjected to heat treatment after sufficiently reducing the hydrogen concentration in the silicon layer in advance, or the silicon layer may be irradiated with laser light. It may be crystallized.

Since silicon has a larger theoretical capacity than graphite, the use of silicon for the active material layer can reduce the thickness to about 1/10 compared to the case of using graphite for the active material layer. It can have a capacity of about. For this reason, it is possible to reduce the weight and size, but if it is formed too thin, the capacity of the secondary battery is reduced. Therefore, the thickness of the active material layer 103 is 50 nm to 10 μm, preferably 100 nm to 5 μm. Further, it is preferable that the capacity of the secondary battery can be increased even when it is not formed thin.

Next, as illustrated in FIG. 2B, a layer 109 containing niobium is formed over the active material layer 103. For example, a niobium oxide layer may be formed as the layer 109 containing niobium. The niobium oxide layer can be formed by vapor deposition using an Nb ₂ O ₅ target. Further, it may be formed by plating, thermal spraying, CVD, sputtering, or the like.

The niobium oxide layer to be formed preferably has a thickness of 1 nm to 1000 nm, more preferably 80 nm to 500 nm. The composition of the formed niobium oxide layer can be represented by Nb _x O _y (x and y are positive integers).

Through the above steps, an electrode of the power storage device can be formed.

(Embodiment 2)
In this embodiment, an electrode of a power storage device which is one embodiment of the present invention and a manufacturing method thereof will be described with reference to FIGS.

FIG. 3 is a diagram illustrating one embodiment of an electrode of a power storage device. 3 includes a current collector 201, an active material layer 203 provided over one surface of the current collector 201, and a layer 209 containing niobium provided over the active material layer 203. Have. Note that the active material layer 203 includes a crystalline silicon region and a whisker-like crystalline silicon region formed over the region.

Next, a method for forming the electrode will be described with reference to FIG.

First, as illustrated in FIG. 4A, a crystalline silicon layer is formed as an active material layer 203 over the current collector 201 by an LPCVD method. The formation of crystalline silicon by the LPCVD method is preferably performed at 550 ° C. or more and below the heat resistant temperature of the LPCVD apparatus and the current collector 201, more preferably 580 ° C. or more and 650 ° C. or less. As the source gas, a deposition gas containing silicon can be used. Examples of the deposition gas containing silicon include silicon hydride, silicon fluoride, or silicon chloride. Typically, there are SiH ₄ , Si ₂ H ₆ , SiF ₄ , SiCl ₄ , Si ₂ Cl _{6, and the} like. . Note that the source gas may be mixed with one or more of rare gases such as helium, neon, argon, and xenon, nitrogen, and hydrogen.

As the current collector 201, the above-described materials listed as materials of the current collector 101 can be used as appropriate.

Note that the active material layer 203 may contain oxygen as an impurity. This is because oxygen is released from the quartz chamber of the LPCVD apparatus and diffuses into the crystalline silicon layer by heating when the crystalline silicon layer is formed as the active material layer 203 by the LPCVD method.

Note that an impurity element that generates carriers, such as phosphorus or boron, may be added to the crystalline silicon layer. Since the crystalline silicon layer to which an impurity element that generates carriers such as phosphorus and boron is added has high conductivity, the conductivity of the electrode can be increased. For this reason, the discharge capacity or the charge capacity can be further increased.

The active material layer 203 includes a crystalline silicon region 203a and a whisker-like crystalline silicon region 203b formed over the region. Note that the interface between the crystalline silicon region 203a and the whisker-like crystalline silicon region 203b is not clear. Therefore, the crystalline silicon region 203a passes through the bottom of the deepest valley among the plurality of protrusions formed between the plurality of protrusions of the whisker-like crystalline silicon region 203b and is parallel to the surface of the current collector. And a whisker-like crystalline silicon region 203b.

The crystalline silicon region 203 a is provided so as to cover the current collector 201. In addition, the whisker-like crystalline silicon region 203b includes a plurality of protrusions provided in an unspecified direction from an unspecified region of the crystalline silicon region 203a.

Note that the plurality of protrusions included in the whisker-like crystalline silicon region 203b may have a columnar shape such as a columnar shape or a prismatic shape, or may have a needle shape such as a cone shape or a pyramid shape. The protrusion may be curved at the top. The plurality of protrusions may be a mixture of columnar protrusions and needle-like protrusions. Further, the protrusions may have irregularities on the surface. By having irregularities on the surface, the surface area of the active material layer can be increased.

In the electrode of the power storage device described in this embodiment, the crystalline silicon layer functioning as the active material layer 203 includes the whisker-like crystalline silicon region 203b; thus, the surface area is increased and the power storage device is discharged at high current density. Capacity or charge capacity can be increased.

Next, as illustrated in FIG. 4B, a layer 209 containing niobium is formed over the active material layer 203. The layer 209 containing niobium can be formed in a manner similar to that of the layer 109 containing niobium in Embodiment 1.

Through the above steps, an electrode of the power storage device can be formed.

(Embodiment 3)
In this embodiment, an electrode of a power storage device that is one embodiment of the present invention and a manufacturing method thereof will be described below.

First, an active material, a conductive additive, a binder and a solvent are mixed to form a slurry. In the preparation of the slurry, the conductive assistant is dispersed in a solvent containing a binder, and the active material is mixed there. At this time, in order to improve dispersibility, it is preferable that the amount of the solvent is suppressed and kneading is performed. Then, a solvent is added and a slurry is produced. The ratios of the active material, the conductive auxiliary agent, the binder and the solvent can be adjusted as appropriate. However, the higher the ratio of the conductive auxiliary agent and the binder, the higher the battery performance per active material amount.

The active material is preferably a material alloyed with lithium, and for example, a material containing silicon, tin, aluminum, or germanium can be used. In this embodiment, granular silicon is used. Note that the smaller the particle size of the granular silicon as the active material, the better the capacity and cycle characteristics, and the particle size is preferably 100 nm or less.

The conductive auxiliary agent is not limited as long as the material itself is an electronic conductor and does not cause a chemical change with other substances in the battery device. For example, carbon materials such as graphite, carbon fiber, carbon black, acetylene black, ketjen black, VGCF (registered trademark), metal materials such as copper, nickel, aluminum or silver, or powders and fibers of these mixtures are applicable. To do. The conductive assistant is a substance that helps conductivity between the active materials, and is a material that is filled between the active materials that are separated from each other to establish conduction between the active materials.

Examples of the binder include starch, polyimide, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, diacetyl cellulose, polyvinyl chloride, polyvinyl pyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, and EPDM (Ethylene Propylene Diene Monomer). , Sulfonated EPDM, SBR (Styrene Butadiene Rubber), butadiene rubber, fluororubber, polyethylene oxide and other polysaccharides, thermoplastic resin or rubber elastic polymer.

Examples of the solvent include water, N-methyl-2-pyrrolidone, and lactic acid ester.

Next, the prepared slurry is applied onto a current collector and dried using a hot plate or an oven. Drying can be performed at about 50 ° C. when an aqueous binder such as SBR is used. Moreover, when using organic binders, such as a polyvinylidene fluoride and a polyimide, it is preferable to make it dry at about 120 degreeC. Then, it punches into a desired shape and performs this drying. The main drying is preferably performed at 170 ° C. for about 10 hours.

As the current collector, for example, a copper foil, a titanium foil, a stainless steel foil, or the like can be used. Moreover, shapes, such as foil shape, plate shape, and net shape, can be used suitably.

A layer containing niobium is formed on the coated electrode manufactured by the above steps. The layer containing niobium can be formed by vapor deposition, for example, and is preferably formed by niobium oxide or niobium nitride.

Through the above steps, an electrode of the power storage device can be formed.

(Embodiment 4)
In this embodiment, the structure of the power storage device will be described with reference to FIGS.

First, a structure of a secondary battery as a power storage device will be described below. Here, the structure of a lithium ion battery, which is a typical example of a secondary battery, will be described.

FIG. 5A is a plan view of the power storage device 151, and FIG. 5B is a cross-sectional view taken along dashed-dotted line AB in FIG. In this embodiment mode, a pouched thin power storage device is shown as the power storage device 151.

A power storage device 151 illustrated in FIG. 5A includes a power storage cell 155 inside an exterior member 153. In addition, terminal portions 157 and 159 connected to the storage cell 155 are provided. As the exterior member 153, a laminate film, a polymer film, a metal film, a metal case, a plastic case, or the like can be used.

As shown in FIG. 5B, the power storage cell 155 includes a negative electrode 163, a positive electrode 165, a separator 167 provided between the negative electrode 163 and the positive electrode 165, and an electrolyte 169.

The negative electrode 163 includes a negative electrode current collector 171 and a negative electrode active material layer 173. The negative electrode active material layer 173 is formed on one or both surfaces of the negative electrode current collector 171.

The positive electrode 165 includes a positive electrode current collector 175 and a positive electrode active material layer 177. The positive electrode active material layer 177 is formed on one or both surfaces of the positive electrode current collector 175.

Further, the negative electrode current collector 171 is connected to the terminal portion 159. The positive electrode current collector 175 is connected to the terminal portion 157. Further, a part of each of the terminal portions 157 and 159 is led out of the exterior member 153.

Note that in this embodiment, a thin pouched power storage device is shown as the power storage device 151; however, various shapes of power storage devices such as a button power storage device, a cylindrical power storage device, and a rectangular power storage device can be used. . Further, although a structure in which the positive electrode, the negative electrode, and the separator are stacked is shown in this embodiment mode, a structure in which the positive electrode, the negative electrode, and the separator are wound may be used.

As the negative electrode current collector 171, the current collector 101 described in Embodiment 1 can be used.

As the negative electrode active material layer 173, similarly to the active material layer 103 described in Embodiment 1, amorphous silicon to which phosphorus is added can be used. Note that silicon may be predoped with lithium. In the LPCVD apparatus, the active material layer 103 formed of silicon is formed while holding the negative electrode current collector 171 with a frame-shaped susceptor, so that the active material layer 103 is simultaneously formed on both surfaces of the negative electrode current collector 171. Therefore, the number of steps can be reduced.

Further, as in Embodiment 1, a layer 179 containing niobium is formed over the negative electrode active material layer 173. The layer 179 containing niobium can be formed using niobium oxide or niobium nitride.

As the positive electrode current collector 175, aluminum, stainless steel, or the like is used. The positive electrode current collector 175 can have a foil shape, a plate shape, a net shape, a film shape, or the like as appropriate.

The positive electrode active material layer 177 can be formed using a material that occludes and releases ions that are carriers of electric charges. For example, LiFeO ₂ , LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiFePO ₄ , LiCoPO ₄ , LiNiPO ₄ , LiMn ₂ PO ₄ , V ₂ O ₅ , Cr ₂ O ₅ , MnO ₂ , and other lithium compounds are used as materials. Can be used. Note that in the case where the carrier ions are alkali metal ions or alkaline earth metal ions other than lithium, as the positive electrode active material layer 177, an alkali metal (for example, sodium or potassium) or an alkali instead of lithium in the lithium compound is used. An earth metal (eg, calcium, strontium, barium, etc.) can also be used.

The solute of the electrolyte 169 is made of a material that can transport lithium ions that are carrier ions and stably exist. Typical examples of the electrolyte solute include lithium salts such as LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiPF ₆ , and Li (C ₂ F ₅ SO ₂ ) ₂ N. When the carrier ion is an alkali metal ion or alkaline earth metal ion other than lithium, an alkaline earth salt such as a sodium salt or potassium salt, a calcium salt, a strontium salt, or a barium salt is used as the solute of the electrolyte 169. A metal salt, beryllium salt, magnesium salt, or the like can be used as appropriate.

As a solvent for the electrolyte 169, a material that can transfer lithium ions (or other carrier ions) is used. The solvent for the electrolyte 169 is preferably an aprotic organic solvent. Typical examples of the aprotic organic solvent include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, acetonitrile, dimethoxyethane, tetrahydrofuran and the like, and one or more of these can be used. In addition, the use of a polymer material that is gelled as a solvent for the electrolyte 169 increases safety including liquid leakage. Further, the power storage device 151 can be reduced in thickness and weight. Typical examples of the polymer material to be gelated include silicon gel, acrylic gel, acrylonitrile gel, polyethylene oxide, polypropylene oxide, and fluorine-based polymer.

Further, a solid electrolyte such as Li ₃ PO ₄ can be used as the electrolyte 169. Further, niobium may be included in the electrolyte 169. Moreover, vinylene carbonate etc. may be included.

The separator 167 uses an insulating porous body. Typical examples of the separator 167 include cellulose (paper), polyethylene, polypropylene, glass fiber, and the like. Further, these materials can be used in a single layer or laminated.

Lithium ion batteries have a small memory effect, a high energy density, and a large discharge capacity. Also, the output voltage is high. For these reasons, it is possible to reduce the size and weight. In addition, there is little deterioration due to repeated charging and discharging, long-term use is possible, and cost reduction is possible.

Next, a capacitor will be described as the power storage device. Typical examples of the capacitor include an electric double layer capacitor and a lithium ion capacitor.

In the case of a capacitor, a material capable of reversibly occluding at least one of lithium ions (or other carrier ions) and anions is used as the positive electrode active material layer 177 of the secondary battery illustrated in FIG. That's fine. Typical examples of the positive electrode active material layer 177 include activated carbon, a conductive polymer, and a polyacene organic semiconductor (PAS).

Lithium ion capacitors have high charge / discharge efficiency, can be rapidly charged / discharged, and have a long life due to repeated use.

When the negative electrode described in Embodiment 1 is used for the negative electrode 163, a power storage device with high discharge capacity or charge capacity and further improved cycle characteristics can be manufactured.

Further, by using the current collector and the active material layer described in Embodiment 1 for the negative electrode of an air battery which is one form of the power storage device, the power storage device has high discharge capacity or charge capacity and further improved cycle characteristics. Can be produced.

As described above, in one embodiment of the present invention, a multilayer structure such as a current collector layer, an active material layer, and a layer containing niobium can be used, whereby the current collector layer, the active material layer, and the layer containing niobium are used. The materials constituting each layer can be bonded to each other to make the structure strong. For this reason, it is difficult for the structure to be destroyed due to the volume change of the active material layer accompanying charge / discharge. As a result, even when a charge / discharge cycle is performed, the active material layer is prevented from being destroyed, so that an increase in resistance inside the battery and a decrease in capacity can be suppressed.

(Embodiment 5)
In this embodiment, application modes of the power storage device described in Embodiment 4 will be described with reference to FIGS.

The power storage device described in Embodiment 4 includes a camera such as a digital camera or a video camera, a digital photo frame, a mobile phone (also referred to as a mobile phone or a mobile phone device), a portable game machine, a portable information terminal, a sound reproduction device, or the like. It can be used for electronic equipment. Further, it can be used for electric propulsion vehicles such as electric vehicles, hybrid vehicles, railway electric vehicles, work vehicles, carts, and electric wheelchairs. Here, an example of an electric propulsion vehicle will be described.

FIG. 6A shows a configuration of a four-wheeled automobile 300 that is one of electric propulsion vehicles. The car 300 is an electric car or a hybrid car. An automobile 300 shows an example in which a power storage device 302 is provided at the bottom. In order to clarify the position of the power storage device 302 in the car 300, FIG. 6B shows the car 300 in which only the outline is shown, and the power storage device 302 provided at the bottom of the car 300. The power storage device described in Embodiment 4 can be used for the power storage device 302. The power storage device 302 can be charged by external power supply using a plug-in technology or a wireless power feeding system.

FIG. 6C illustrates a configuration of a motor boat 1301 that is one of the electric propulsion vehicles. FIG. 6C illustrates the case where the motor boat 1301 includes the power storage device 1302 on the side of the hull. The power storage device described in Embodiment 4 can be used for the power storage device 1302. The power storage device 1302 can be charged by external power supply using plug-in technology or a wireless power feeding system. A power supply device for charging the motor boat 1301 (that is, charging the power storage device 1302) can be provided, for example, in a mooring facility for mooring a ship in a harbor.

FIG. 6D illustrates a structure of an electric wheelchair 1311 that is one of the electric propulsion vehicles. FIG. 6D illustrates the case where the electric wheelchair 1311 includes the power storage device 1312 at the bottom thereof. The power storage device described in Embodiment 4 can be used for the power storage device 1312. The power storage device 1312 can be charged by external power supply using plug-in technology or a wireless power feeding system.

(Embodiment 6)
In this embodiment, an example in which a secondary battery, which is an example of a power storage device according to one embodiment of the present invention, is used in a wireless power feeding system (hereinafter referred to as an RF power feeding system) is described with reference to FIGS. This will be described with reference to the block diagram. In each block diagram, the components in the power receiving device and the power feeding device are classified by function and shown as blocks independent of each other, but the actual components are difficult to completely separate for each function, One component may be related to a plurality of functions.

First, the RF power feeding system will be described with reference to FIG.

The power receiving device 600 is an electronic device or an electric propulsion vehicle that is driven by power supplied from the power feeding device 700, but can be appropriately applied to other devices that are driven by power. Representative examples of electronic devices include cameras such as digital cameras and video cameras, digital photo frames, mobile phones (also referred to as mobile phones and mobile phone devices), portable game machines, portable information terminals, sound playback devices, display devices, There are computers. Typical examples of the electric propulsion vehicle include an electric vehicle, a hybrid vehicle, a railway electric vehicle, a work vehicle, a cart, and an electric wheelchair. In addition, the power feeding device 700 has a function of supplying power to the power receiving device 600.

In FIG. 7, the power receiving device 600 includes a power receiving device unit 601 and a power load unit 610. The power receiving device portion 601 includes at least a power receiving device antenna circuit 602, a signal processing circuit 603, and a secondary battery 604. The power feeding device 700 includes at least a power feeding device antenna circuit 701 and a signal processing circuit 702.

The power receiving device antenna circuit 602 has a function of receiving a signal transmitted from the power feeding device antenna circuit 701 or transmitting a signal to the power feeding device antenna circuit 701. The signal processing circuit 603 processes a signal received by the power receiving device antenna circuit 602 and controls charging of the secondary battery 604 and supply of power from the secondary battery 604 to the power load portion 610. The signal processing circuit 603 controls the operation of the power receiving device antenna circuit 602. That is, the intensity, frequency, and the like of a signal transmitted from the power receiving device antenna circuit 602 can be controlled. The power load unit 610 is a drive unit that receives power from the secondary battery 604 and drives the power receiving device 600. Typical examples of the power load unit 610 include a motor, a drive circuit, and the like, but a device that receives other power and drives the power receiving device can be used as appropriate. The power feeding device antenna circuit 701 has a function of transmitting a signal to the power receiving device antenna circuit 602 or receiving a signal from the power receiving device antenna circuit 602. The signal processing circuit 702 processes a signal received by the power feeding device antenna circuit 701. The signal processing circuit 702 controls the operation of the power feeding device antenna circuit 701. That is, the intensity, frequency, and the like of a signal transmitted from the power feeding device antenna circuit 701 can be controlled.

The secondary battery according to one embodiment of the present invention is used as the secondary battery 604 included in the power receiving device 600 in the RF power feeding system described with reference to FIG.

By using the secondary battery according to one embodiment of the present invention for the RF power feeding system, a discharge capacity or a charge capacity (also referred to as an amount of stored electricity) can be increased as compared with a conventional secondary battery. Therefore, the time interval of wireless power feeding can be extended (the trouble of repeatedly feeding power can be saved).

Further, by using the secondary battery according to one embodiment of the present invention for the RF power feeding system, if the discharge capacity or the charge capacity capable of driving the power load portion 610 is the same as the conventional one, the power receiving device 600 can be reduced in size. And weight reduction is possible. Therefore, the total cost can be reduced.

Next, another example of the RF power feeding system will be described with reference to FIG.

In FIG. 8, the power receiving device 600 includes a power receiving device unit 601 and a power load unit 610. The power receiving device portion 601 includes at least a power receiving device antenna circuit 602, a signal processing circuit 603, a secondary battery 604, a rectifier circuit 605, a modulation circuit 606, and a power supply circuit 607. The power feeding device 700 includes at least a power feeding device antenna circuit 701, a signal processing circuit 702, a rectifier circuit 703, a modulation circuit 704, a demodulation circuit 705, and an oscillation circuit 706.

The power receiving device antenna circuit 602 has a function of receiving a signal transmitted from the power feeding device antenna circuit 701 or transmitting a signal to the power feeding device antenna circuit 701. When a signal transmitted from the power feeding device antenna circuit 701 is received, the rectifier circuit 605 has a role of generating a DC voltage from the signal received by the power receiving device antenna circuit 602. The signal processing circuit 603 has a function of processing a signal received by the power receiving device antenna circuit 602 and controlling charging of the secondary battery 604 and supply of power from the secondary battery 604 to the power supply circuit 607. The power supply circuit 607 has a role of converting a voltage stored in the secondary battery 604 into a voltage necessary for the power load portion 610. The modulation circuit 606 is used when a certain response is transmitted from the power receiving apparatus 600 to the power feeding apparatus 700.

By including the power supply circuit 607, the power supplied to the power load portion 610 can be controlled. For this reason, it is possible to reduce that an overvoltage is applied to the power load part 610, and deterioration and destruction of the power receiving apparatus 600 can be reduced.

In addition, by including the modulation circuit 606, a signal can be transmitted from the power receiving device 600 to the power feeding device 700. Therefore, the charging amount of the power receiving device 600 is determined, and when a certain amount of charging is performed, a signal is transmitted from the power receiving device 600 to the power feeding device 700, and power feeding from the power feeding device 700 to the power receiving device 600 is stopped. be able to. As a result, the maximum charge count of the secondary battery 604 can be increased by not setting the charge amount of the secondary battery 604 to 100%.

The power feeding device antenna circuit 701 has a function of transmitting a signal to the power receiving device antenna circuit 602 or receiving a signal from the power receiving device antenna circuit 602. When a signal is transmitted to the power receiving device antenna circuit 602, the signal processing circuit 702 is a circuit that generates a signal to be transmitted to the power receiving device. The oscillation circuit 706 is a circuit that generates a signal having a constant frequency. The modulation circuit 704 has a role of applying a voltage to the power feeding device antenna circuit 701 in accordance with the signal generated by the signal processing circuit 702 and the signal of a certain frequency generated by the oscillation circuit 706. By doing so, a signal is output from the power feeding device antenna circuit 701. On the other hand, when a signal is received from the power receiving device antenna circuit 602, the rectifier circuit 703 has a role of rectifying the received signal. The demodulation circuit 705 extracts a signal sent from the power receiving device 600 to the power feeding device 700 from the signal rectified by the rectifying circuit 703. The signal processing circuit 702 has a role of analyzing the signal extracted by the demodulation circuit 705.

Note that any circuit may be provided between the circuits as long as RF power feeding can be performed. For example, after the power receiving apparatus 600 receives a signal and generates a DC voltage by the rectifier circuit 605, the constant voltage may be generated by a circuit such as a DC-DC converter or a regulator provided in a subsequent stage. By doing so, it is possible to suppress application of an overvoltage inside the power receiving device 600.

The secondary battery according to one embodiment of the present invention is used as the secondary battery 604 included in the power receiving device 600 in the RF power feeding system described in FIG.

By using the secondary battery according to one embodiment of the present invention for the RF power feeding system, the discharge capacity or the charging capacity can be increased as compared with the conventional secondary battery, so that the time interval of wireless power feeding can be extended. (It can save the trouble of supplying power many times).

Further, by using the secondary battery according to one embodiment of the present invention for the RF power feeding system, if the discharge capacity or the charge capacity capable of driving the power load portion 610 is the same as the conventional one, the power receiving device 600 can be reduced in size. And weight reduction is possible. Therefore, the total cost can be reduced.

Note that when the secondary battery according to one embodiment of the present invention is used for the RF power feeding system and the antenna circuit 602 for the power receiving device and the secondary battery 604 are stacked, the secondary battery 604 is deformed by charging and discharging of the secondary battery 604 It is preferable that the impedance of the power receiving device antenna circuit 602 is not changed by the change in the shape of the antenna accompanying the deformation. This is because if the impedance of the antenna changes, there is a possibility that sufficient power is not supplied. For example, the secondary battery 604 may be loaded into a metal or ceramic battery pack. At that time, it is desirable that the power receiving device antenna circuit 602 and the battery pack be separated from each other by several tens of μm or more.

In this embodiment, the frequency of the charging signal is not particularly limited, and any band may be used as long as power can be transmitted. The frequency of the charging signal may be, for example, a 135 kHz LF band, a 13.56 MHz HF band, a 900 MHz to 1 GHz UHF band, or a 2.45 GHz SHF band.

There are various signal transmission methods such as an electromagnetic coupling method, an electromagnetic induction method, an electromagnetic resonance method, and a microwave method, which may be selected as appropriate. However, in order to suppress energy loss due to moisture or other foreign matter such as rain or mud, a low frequency band, specifically, a HF band of 3 MHz to 30 MHz, a MF band of 300 kHz to 3 MHz, LF It is desirable to use an electromagnetic induction method or a resonance method using a frequency of 30 kHz to 300 kHz which is a band and a frequency of 3 kHz to 30 kHz which is a VLF band.

This embodiment can be implemented in combination with the above embodiment.

In this example, a secondary battery which is one embodiment of the present invention will be described. In this example, a secondary battery which is one embodiment of the present invention and a comparative secondary battery (hereinafter referred to as a comparative secondary battery) were manufactured, and the battery characteristics were compared.

<Production process of secondary battery electrode>
First, a process for manufacturing an electrode of a secondary battery will be described.

By forming an active material layer on the current collector, a secondary battery electrode was formed.

Titanium was used as a material for the current collector. As the current collector, a sheet-shaped titanium foil (also referred to as a titanium sheet) having a thickness of 100 μm was used.

As the active material layer, an amorphous silicon layer to which phosphorus was added was used.

An amorphous silicon layer to which phosphorus as an active material layer was added was formed by plasma CVD on a titanium foil as a current collector. The formation of an amorphous silicon layer to which phosphorus is added by plasma CVD is performed using silane and phosphine as material gases, introducing a silane flow rate of 60 sccm and a phosphine flow rate of 110 sccm, and setting the pressure in the reaction chamber to 133 Pa. Then, the temperature in the reaction chamber was adjusted to 400 ° C. for the upper heater setting and 500 ° C. for the lower heater setting to form a film.

The amorphous silicon layer to which phosphorus was added obtained by the above process was used as the active material layer of the secondary battery.

Next, a niobium oxide layer was formed on the formed active material layer by an evaporation method. Niobium oxide having a composition of Nb ₂ O ₅ was used as a vapor deposition source, and vapor deposition was performed in a vacuum. Further, the composition of the niobium oxide layer was measured using X-ray photoelectron spectroscopy (XPS). As a result, it was confirmed that the formed niobium oxide layer was formed with substantially the same composition as Nb ₂ O ₅ which is the vapor deposition source.

Through the above steps, an electrode of a secondary battery was produced.

<Production process of secondary battery>
Next, a manufacturing process of the secondary battery of this example will be described.

A secondary battery was fabricated using the electrode obtained by the above process. Here, a coin-type secondary battery was manufactured. A method for manufacturing a coin-type secondary battery will be described below with reference to FIGS.

As shown in FIG. 9, the coin-type secondary battery includes an electrode 204, a reference electrode 232, a separator 210, an electrolytic solution (not shown), a housing 206, and a housing 244. In addition, a ring-shaped insulator 220, a spacer 240, and a washer 242 are provided. The electrode 204 was manufactured by the above process, and an electrode in which an active material layer and a layer containing niobium were provided over a current collector was used. In this example, titanium foil was used as a current collector, and the active material layer was formed using a laminated structure including the amorphous silicon layer to which phosphorus described in Embodiment 1 was added and a niobium oxide layer. As the reference electrode 232, lithium metal (lithium foil) was used. Polypropylene was used for the separator 210. The housing 206, the housing 244, the spacer 240, and the washer 242 were made of stainless steel. The housing 206 and the housing 244 have a function of electrically connecting the electrode 204 and the reference electrode 232 to the outside.

The electrode 204, the reference electrode 232, and the separator 210 were impregnated with an electrolytic solution. Then, as shown in FIG. 9, the electrode 204, the separator 210, the ring insulator 220, the reference electrode 232, the spacer 240, the washer 242, and the housing 244 are laminated in this order with the bottom of the housing 206 facing down. A coin-type secondary battery was manufactured by caulking the housing 206 and the housing 244 with a “coin crimping machine”.

As the electrolytic solution, a solution obtained by dissolving LiPF _{6 in} a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) was used.

<Production process of comparative secondary battery electrode>
Next, a process for manufacturing an electrode of the comparative secondary battery will be described. The secondary battery which is one embodiment of the present invention and the comparative secondary battery are different in the manufacturing process of the active material layer. Since other configurations are common, configurations of a substrate, a current collector, and the like are omitted.

As an active material layer of the comparative secondary battery, an amorphous silicon layer to which phosphorus was added was used in a single layer structure.

<Production process of comparative secondary battery>
Next, a manufacturing process of the comparative secondary battery will be described.

As described above, an active material layer was formed on the current collector, and an electrode of a comparative secondary battery was formed. A comparative secondary battery was produced using the obtained electrode. The production of the comparative secondary battery was performed in the same manner as the production of the secondary battery except for the electrode forming method.

<Characteristic comparison of secondary battery and comparative secondary battery>
About the secondary battery produced as mentioned above and a comparison secondary battery, the battery characteristic was compared using the charging / discharging measuring machine. The constant current method is adopted for the measurement of charging / discharging, only 0.05 mA is charged for the first time, and charging and discharging is performed with a current of 0.15 mA after the charging, and the upper limit voltage is 1.0 V and the lower limit voltage is 0.03 V. went. The capacity limit was 2000 (mAh / g), and the measurement was performed at room temperature. The results are shown in Table 1 and FIG.

Table 1 shows the ratio of the lithium release amount to the lithium storage amount in various charge / discharge cycle numbers, that is, the results of the evaluation of the charge / discharge efficiency. From this result, the secondary battery using the electrode formed by forming niobium oxide on the active material layer is compared with the comparative secondary battery using the electrode manufactured without forming niobium oxide on the active material layer. Thus, it was found that the charge / discharge efficiency was very high, and that the irreversible capacity was almost zero. The discharge capacity (mAh / g) was calculated assuming that the weight of the active material layer of the secondary battery and the comparative secondary battery was 0.255 mg.

FIG. 10 shows the result of the lithium release amount with respect to the charge / discharge cycle. From this result, the secondary battery using the electrode formed by forming niobium oxide on the active material layer is compared with the comparative secondary battery using the electrode manufactured without forming niobium oxide on the active material layer. Thus, it was found that even when the number of charge / discharge cycles was increased, no decrease in lithium release capacity was observed.

From the results shown in Table 1 and FIG. 10, the secondary battery using the electrode formed by forming niobium oxide on the active material layer was compared using the electrode manufactured without forming niobium oxide on the active material layer. It was found that the charge / discharge efficiency and cycle characteristics were improved as compared with the secondary battery.

DESCRIPTION OF SYMBOLS 101 Current collector 103 Active material layer 109 Niobium containing layer 151 Power storage device 153 Exterior member 155 Power storage cell 157 Terminal portion 159 Terminal portion 163 Negative electrode 165 Positive electrode 167 Separator 169 Electrode 171 Negative electrode current collector 173 Negative electrode active material layer 175 Positive electrode current collector Body 177 Positive electrode active material layer 179 Layer 201 containing niobium Current collector 203 Active material layer 203a Crystalline silicon region 203b Crystalline silicon region 204 Electrode 206 Housing 209 Layer containing niobium 210 Separator 220 Ring insulator 232 Reference electrode 240 Spacer 242 Washer 244 Case 300 Car 302 Power storage device 600 Power receiving device 601 Power receiving device unit 602 Power receiving device antenna circuit 603 Signal processing circuit 604 Secondary battery 605 Rectifier circuit 606 Modulating circuit 607 Power source circuit 610 Power source load unit 700 Collector 701 power feeding device antenna circuit 702 a signal processing circuit 703 rectifying circuit 704 modulation circuit 705 demodulation circuit 706 oscillation circuit 1301 motorboat 1302 power storage device 1311 electric wheelchair 1312 power storage device

Claims (4)

A current collector,
An active material layer formed on the current collector and made of a material alloyed with lithium;
A power storage device using an electrode formed on the active material layer and including a layer containing niobium.   2. The power storage device according to claim 1, wherein the layer containing niobium is formed of niobium oxide or niobium nitride.   3. The power storage device according to claim 1, wherein the material alloyed with lithium is silicon, tin, aluminum, or germanium. A current collector,
An active material layer formed of a material alloyed with lithium on the current collector;
A negative electrode having a layer containing niobium formed on the active material layer,
An electrolyte formed in contact with the negative electrode;
A power storage device comprising: a positive electrode facing the negative electrode with the electrolyte interposed therebetween.